Pivoted tool joint construction



Jan. 12, 1960 H. M. PORTER 2,920,927

PIVOTED TOOL JOINT CONSTRUCTION III Filed July 30, 1956 K F t P! INVENTOR. HARRY lvl. PORTER BY Wyh a/no/ MW ATTORN EYS United States Patent 2,920,927 r PIVOTED TOOL JOINT CONSTRUCTION M. Porter, Utica, N.Y., assignor, by mesne assignments, to Kelsey-Hayes Company, Detroit, Mich., a corporation of Delaware Application July 30,1956, Serial No. 600,795, r

2 Claims. (Cl. 308-2) pin. In making such a hand tool the members are first forged to a shape which conforms in general to the desired finished configuration. Machining operations are then performed to form the members to the finished configuration. One of these machine operations is the preparation of a pivot region for mutual bearing support of the two members and for insertion of the pivot pin. The present invention is directed to' the preparation of this region.

In preparation of the pivot region, an end mill is brought down against the jaw member and a well is 1 formed in the pivot region of the jaw member. This Well has a flat bearing surface which lies in a plane substantially normal to the pivot pin. The well areas are analgous to the interfitting joint portions in amortised joint. Thus, the remaining portions fit together into a mutually pivoted joint construction. To hold the joint together and provide a mutual pivot axis, a rivet, which serves as a pivot pin, is provided. A hole is drilled through the two bearing surfaces. Usually the hole is chamfered, and the rivet hammered, or hot formed, to fill the chamfer, and thus bind the two half-plier members together. Such riveting produces considerable pressure. If the bearing surfaces are fully mated and smooth, then very little breaking-in will be required.

Hand tools made in conformance with prior known practice have certain disadvantages. The end mills wear most rapidly at the peripheral extremities of the cutting edge. Bearing surfaces formed by such a worn end mill cutter have a burr at the peripheral extremity when the cut is on a fully exposed area, and have chamfered corners when the cut is into a body in such a manner that side walls remain. When the bearing surfaces have such burrs or chamfers the hand tool must be broken in after the jaw members are joined together. Thus, a new hand tool will be stiif and difficult to manipulate until broken in by wear. After the joint has been worn in, the joint is loose and the hand tool loses some of the rigidity and accuracy which it was intended to have.

It has been discovered that if the end mill cutter is formed with downwardly projecting extensions at the peripheral extremities of the cutting edges, the bearing surface may be undercut at its extremity in the vicinity of the side wall and chamfered over the remainder of the extremity. A chamfered portion of the bearing surface completely eliminates burrs while the undercut portion eliminates a buildup in the corner of the wall. Therefore, the need for break in is completely eliminated.

Accordingly, one of the principal object of this invention is to provide a hand tool which operates freely and does not require break in.

Another object of this invention is to provide an end 2,920,927 Patented Jan. 12, 1960 mill cutter which will form such a bearing surface which needs no break in.

An additional object of this invention ,is to provide a hand tool in which a long lasting pivot may be formed and in which the rigidity and firmness of the pivot as originally formed is maintained throughout the life of the tool. V

Other objectsand a fuller understanding of the invention may be had by referring to the following description and claims, taken in conjunction with theac companying drawing, in which:

Figure 1 is a plan view of a jaw member of-a plier hand tool and a phantom view of a complemental jaw member;

Figures 2, 3 and 4 are sectional views as seen from the plane indicated by the line 4-4 of Figure 1 showing progressive steps in preparing the well in the pivot region of the jaw member;

Figure 5 is a fragmentary sectional view as seen from the plane indicated by line 5-5 of Figure 1 showing a finished well in a jaw member; and

Figure 6 is a fragmentary side elevational view of a hand .tool.

Referring to the drawing and to Figure 1 in particular, a hand tool having forged jaw members 10, 20 is disclosed, the jaw member 20 is shown in phantom. The machining operations performed on the jaw members, insofar as this invention is concerned, are identical. For simplicity and clarity of illustration, the operation will be described with respect to'the jaw member 10.

The jaw member 10 is forged to a generally finished form with a central generally circular pivot portion 17. The jaw member 10 also has a handle portion 27 and a work portion 37. The present invention is directed to an improved connection of pivot portions of .the'jaw members 10, 20 and to preparation of this pivot portion or region 17.

A pivot hole 11 is drilled along the axis of the pivot portion 17. An end mill cutter 12 is then brought into contact with the jaw member 10, Figure 3. The cutter 12 has cutting blades 13. Extensions, or teeth, 14 are provided at the peripheral extremities of the cutting blades 13. The cutting tool 12 is brought down until approximately one-half the metal is removed from the pivot portion 17 of the forging. A well 15 is formed by this operation.

A plane bearing surface 21 forms the bottom of the well 15. The bearing surface 21 lies in a plane which is substantially normal to the axis of the pivot region 17 and the pivot hole 11. Side walls 22, 23 are simultaneously formed by the same cutting operation. The side walls 22, 23 define the peripheral limits of the well 15. The side walls each define a segment of a cylinder. The side walls 22, 23 form guides for the pivot portion of the complemental jaw member 20.

When the hand tool is assembled the bearing surface 21 coacts with a complemental bearing surface. Bearing surfaces formed in accordance with prior known methods frequently had a ridge or burrs formed at the peripheral extremity. These ridges prevented full facial contact of the complemental bearing surfaces.

One of the outstanding advantages of the present invention is formed by the absolute absence of any corner chamfer between bearing surface 21 and side walls 22 and 23, and the elimination of any burr or ridge about the remainder of the periphery of the bearing surface. Note the cutter blades 13. Preferably, every blade 13 is formed with depending extremities, or teeth areas, 14. A negative chamfer, or recess 25, is produced by the action of the teeth 14 of the cutter 12. The recess 25 is formed at the peripheral extremity of the bearing surface 21. Thus, the bearing surface is intentionally under cut at its peripheral portion to assure the formation of a flat bearing surface having no peripheral ridge.

When jaw members made in accordance with prior known methods are connected together, the bearing surfaces generally do not come into facial contact. Pe ripheral ridges prevent engagement of the bearing surfaces. 7 his necessary to break the tool in by moving the jaw members relatively back and forth until the ridges were sufiiciently Worn away to permit facial bearing contact.

When two chamfered bearing surfaces 21 made in accordance with the present invention are placed in face to face engagement, uniform surface'contact is assured and a tool is formed which is easy to' operate. The ease of operation corresponds to prior known hand tools which have been used for manyyears, yetthe firmness of the joint is better than that of even new prior tools made in accordance with prior practice. I Further; the firmness remains throughout the life of the tool While in prior known pivot hand tools jointsbecome loose and accuracy of the tool is lost.

The jaw members are held in operative relationship by a conventional pivot pin rivet 26 provided in the conventional manner. Placement of the rivet produces the holding pressure that is intended to keep the jaw members in close alignment.

There has thus been described an improved hand tool in which a non-binding improved pivot joint is formed. There has also been described an improved cutting tool for forming such a joint and the method of forming an improved pivot for a hand tool.

Although the invention has been described in its preferred form with a certain degree of particularity, it is understood that the present disclosure of the preferred form has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention as hereinafter claimed.

What is claimed is:

1. In a pivoted hand tool having a pivot portion composed of firs-t and second bearing wells nested together, the provision of a full bearing surface contact in snug relationship with all internal wall junctions undercut to prevent corner junction binding between the members.

2. A pivoted hand tool, comprising, first and second lever members, each lever member having a work head portion, a handle portion, and an intermediate pivot portion, said pivot portion defined by a bearing wall with a flat bearing face, a first shoulder wall between said work head portion and said pivot wall bearing face, a second shoulder wall between said handle portion and said pivot wall bearing face, said first and second shoulder walls being oppositely disposed with open spacings there between, said bearing wall disposed to one side of the pivot area, said bearing wall and the first and second shoulder Walls thereby defining a pivot well, said first and second lever members mated together with the pivot wells 'intermeshed,'the juncture between the first and second shoulder walls and the bearing face of each said lever member being recessed to a greater degree than an angular junction in the form of a negative chamfer, and a rivet extending through the mutual pivot portions, whereby the bearing surfaces are in mutual contact upon originally riveting the first and second lever members together and the junction areas of the pivot area are out of mutual contact.

References Cited in the file of-this patent UNITED STATES PATENTS 397,389 Richards Feb. 5, 1889 1,183,525 Billings May 16, 1916 1,596,470 Way Aug. 17, 1926 1,639,269 Potschuer Aug. 16, 1927 2,129,418 G356 Sept. 6, 1938 2,535,398 Economous Dec. 26, 1950 2,614,894 Brock Oct. 21, 1952 

